The .beta.-lactam antibiotics constitute a very useful family of antibiotics owing to their broad antibacterial spectrum. The present inventors have developed orally effective cephalosporin derivatives which have, at the 3-position of the cephem nucleus, a thioalkylthio side chain substituted by a heterocyclic group, disclosed in U.S. patent application Ser. No. 07/729,413, filed on Jul. 12, 1991, (now U.S. Pat. No. 5,214,037) and EPO Application Publication No. 0 467 647 A2, (Jan. 22, 1992). However, because of the increase in low-sensitive bacteria or the appearance of resistant bacteria, further development of effective antibiotics is continuously needed.
The present inventors have made intensive studies with the purpose of developing novel and effective antibiotics and synthesized thioalkylthio carbacephalosporin derivatives having at the 3-position of the 1-carbacephem nucleus a thioalkylthio side chain optionally substituted by a heterocyclic group, said derivatives corresponding to those disclosed in the aforementioned U.S. patent application Ser. No. 07/729 413, now U.S. Pat. No. 5,214,037 and EPO Application Publication No. 0 467 647 A2 (Jan. 22, 1992). When these carbacephalosporin derivatives were evaluated for antibiotic properties, certain compounds, for example, those having a thioalkylthio side chain substituted with an optionally substituted triazolyl, showed preferable properties in terms of antibiotic activity, binding ability to plasma proteins and the like.